Learn About Local
Geology

2. Window
into the Jurassic World by Nicholas G. McDonald,
Published by Friends of Dinosaur State Park and Arboretum, Inc.

3. (for younger kids) The Natural
History and Resources of Western Massachusetts by Stan Freeman and
Mike Nasuti, Published by Hampshire House Publishing Co.

The above diagram shows the general geology of the
area surrounding the Nash Dinosaur Track Site.
The cross section runs north to south.

ROCK LAYERS OF THE CONNECTICUT RIVER VALLEY NEAR
THE NASH DINOSAUR TRACK SITE

(Layers are listed from upper to
lower layers)

3. GLACIAL DEPOSITS
– During the last major glacial period the glaciers
stripped away the top geological sediments of the valley. Later, as the
glaciers melted away, they left behind a layer of sediment on top of
the underlining rocks . This layer of glacial material varies from zero
to 100 feet in depth . This is the layer that makes up most of the
surface of the Connecticut River Valley floor.

2. ANCIENT SEDIMENTARY
ROCK LAYERS - These rock layers are made up of a series of
sedimentary layers interspersed with two lava flow layers. All are laid
down on top of the basement rock. It is in two of these sedimentary
layers that one finds dinosaur tracks.

e. *Portland Formation* -
A layer of sandstone to shale to siltstone sized particles that were
laid down in an arid mud flat with oases environment. This is the layer
that contains the most dinosaur tracks and skeletons. Two fragmentary
theropod skeletons have been found in the Portland Formation rocks, as
have been numerous prosauropod skeletons and an early crocodile. It
also contains fossil fish, plants, invertebrate trace fossils, ripple
marks, rain drop impressions and mud cracks. *This is the layer in
which the Nash Dinosaur Track Site is located*.

d. Hampden Basalt and Granby
Tuff Formations - This is the last of two basalt lava flow that
make up the Mount Holyoke Range. Like the underlying Holyoke Basalt,
the Hampden Basalt came to the surface and flowed out over the basin
sediments before hardening. The Granby Tuff is a thin layer of volcanic
ash and sediment that is intertwined with the Hampden Basalt . There
are no fossils found in this formation .

c. East Berlin Formation -
A layer of shale to siltstone sized particles that was laid down
primarily in an arid mud flat with oases environment. There are fossil
fish found in the sediments that were deposited in the ancient oasis
lakes and dinosaur tracks which were formed in the lake shore deposits.
This is not the layer where the most dinosaur tracks are found.

b. Holyoke Basalt Formation
- This is the first of two basalt lava flows that make up the Mt.
Holyoke Range. Based on its chemical composition, geologists know that
it erupted more like the fast-flowing rivers of lava on the Hawaiian
Islands than the highly explosive eruptions of volcanoes like Mt. Saint
Helens. The lava came to the surface and flowed out over the New Haven
Arkose Formation before solidifying. There are no fossils found in this
formation .

a. New Haven/Sugarloaf Arkose
Formation - ( North of the Mount Holyoke Range this formation is
called the Sugarloaf Arkose, but on the south side, around the Nash
Dinosaur Track Site and south, it is called the New Haven Arkose . ) It
is a layer of conglomerate to sandstone sized particles deposited by
flowing streams. The stone is often reddish in color and contains some
scrappy skeletal material . Some of the fossils found in this formation
are the crocodile-like phytosaur, small lizard-like reptiles, and the
plant-eating aetosaurs .

1. BASEMENT ROCK
- The basement rock is a complex mixture of igneous and metamorphic
rock. It is made up of ancient ocean sediments and igneous rocks.

ENVIRONMENT OF THE NASH DINOSAUR
TRACK SITE
AT THE TIME OF THE DINOSAURS

This is a mural of
what the Nash Dinosaur Track Site looked like at the time of the
dinosaurs.
It was a very different place then than what it is today.
The view is looking south toward Springfield, MA.

The Connecticut River Valley of
Massachusetts and Connecticut is part of an ancient rift valley system
called the Newark Supergroup . It stretches from Newfoundland, Canada
to Florida, USA. This rift valley system is made up of a series of
smaller rift basins that formed when the Pangea continent separated .
The Connecticut River Valley is made up of the Deerfield Basin (north
of the Mount Holyoke mountain range) and the Hartford Basin (south of
the Mount Holyoke mountain range). The Nash Dinosaur Track Site is
located at the northern end of the Hartford Basin .

The climate of the Deerfield and
Hartford basins was semi-arid and hot most of the year, similar to that
of the rift valley of East Africa today. However, each year there was a
monsoon season that usually brought a lot of rain to the area,
especially to the mountains to the east and to the west. The rain that
fell in the mountains was carried into the valley in streams and as
sheet floods, and at certain times it collected into large lakes that
would cover much of the valley floor . (There was no Connecticut River
at the time). During the dry season, the lakes would recede and the
dinosaurs would have roamed the valley, leaving their imprints in the
mud to harden. However, the lakes rarely completely dried up, and
during the dry season remnant lakes would form oasis areas around which
life would have congregated for food and water .

The mountains to the west of the
valley were the early Appalachian Mountains . The mountains to the east
were formed by large faults that uplifted the land to the east of the
valley as the valley subsided . The sediments that filled the valley in
which the Nash Dinosaur Track Site is located were eroded from these
mountains east and west. The Hartford and Deerfield rift valley basins
were probably bigger than what they are today. Currently, the basin is
about 20 miles wide and stretches from what is today the Massachusetts
and Vermont border south to Long Island Sound. In some of the valley's
sedimentary layers (the East Berlin and the Portland) we find the
impressions of dinosaur tracks.

Eventually the rift valley
completely filled with sediment and the erosional processes slowly
began to work . Much later, huge glaciers, up to 1 mile thick, moved
across New England from north to south, speeding up the erosion
process. The glaciers removed the upper geological layers and
re-exposed the lower geological layers with the dinosaur tracks in
them. However, when the ice melted, large deposits of glacial debris
were left behind on top of the sedimentary rocks containing the
dinosaur tracks.

Today only parts of the old mud
flat layers are exposed. One place where one may find dinosaur tracks
is along the edge of streams where streams have eroded down through the
glacial material . Also, one may find dinosaur tracks where areas of
the old mud flat layers stick up above the surrounding glacial material
. This is why the Nash Dinosaur Track Site is exposed. Finally, one may
find tracks where excavation work digs down through the glacial
material and exposes the underlying mud flat layers .

EDWARD HITCHCOCK'S 1858
GEOLOGY OF THE VALLEY

The diagram shown above was created for the 1858 Ichnology of New
England by Edward Hitchcock. The diagram runs east to west . The
geology is simplistic compared to today's knowledge, but it has the
right idea about a number of things .